4 stroke - Gas in Oil.

[Jeff115Merc]

I have a 2003 115hp Merc. I service the engine regularly and it runs just fine but when I check the oil, I find, I have to change the oil due to excessive gas. When I look at the dip stick, it appears to be a quart high in the span of a month. How is Gas getting into the crankcase when its fuel injected and runs fine?

 

[JB]

Re: 4 stroke - Gas in Oil.

Hi. Jeff.
:welcome:

Look here: http://forums.iboats.com/engine-fre...4stroke-making-oil-willy-b-wright-158085.html

 

[Al Kungel]

Re: 4 stroke - Gas in Oil.

My Yamaha 8 HT all of a sudden was "making oil" the problem was the thermostat was broken (stuck on open) the engine was not running hot enough causing gas to leak down.

 

[bilge rat jim]

Re: 4 stroke - Gas in Oil.

You've got a faulty fuel pump diaphragm. The fuel pump is powered by a push rod from the camshaft, and a rip in the diaphragm will allow fuel into the rocker cover on the cylinder head, where it mixes with the engine oil and returns to the oil sump. I would inspect the fuel pump and repair it before using the outboard again, fuel in the crankcase is just an explosion waiting to happen. Here is the parts diagram for your outboard:
Mercury, Mercruiser, Force, etc. - FUEL PUMP - 115 EFI (4-STROKE)

 

[Jeff115Merc]

Re: 4 stroke - Gas in Oil.

You've got a faulty fuel pump diaphragm. The fuel pump is powered by a push rod from the camshaft, and a rip in the diaphragm will allow fuel into the rocker cover on the cylinder head, where it mixes with the engine oil and returns to the oil sump. I would inspect the fuel pump and repair it before using the outboard again, fuel in the crankcase is just an explosion waiting to happen. Here is the parts diagram for your outboard:
Mercury, Mercruiser, Force, etc. - FUEL PUMP - 115 EFI (4-STROKE)

Thanks for the info and I will disassemble the pump for an inspection.